The invention relates in general to drive shaft assemblies, such as are commonly found in the drive train systems of vehicles. In particular, this invention relates to improved balancing in such a vehicular drive shaft assembly.
A vehicle drive shaft assembly delivers torque from a driving member, such as a transmission output shaft, to a driven member, such as an input shaft to an axle assembly. In many vehicles, a drive shaft assembly includes, in part, a hollow cylindrical drive shaft tube with a tube yoke welded to each end. Each tube yoke connects to and forms a part of a universal joint (U-joint). These U-joints help provide the rotational driving connection while accommodating a limited amount of angular misalignment between the rotational axes of the members.
Often times, due to manufacturing variations, the drive shaft tube with welded-on yokes will not be balanced about the axis of rotation for this assembly. This is especially true of the yokes, which have a much more complex shape than the tube. An out of balance drive shaft can induce excessive vibrations in the drive line, which is undesirable.
A conventional way to assure a balanced drive shaft assembly is to mount a drive shaft on a balancing machine and spin it to test its balance about the axis of rotation. If found out of balance, small balancing weights are welded to the outer surface of the drive shaft tube or yokes on the lighter weight side. But this drive shaft balancing technique tends to create stress risers at the weld locations for the balance weights, which may tend to reduce the fatigue life of the drive shaft. It also creates the possibility that a balance weight may be thrown off during vehicle operation, causing the drive shaft to operate out of balance.
Thus, it is desirable to have a balanced drive shaft for use in a vehicle without the drawbacks associated with conventional drive shaft balancing.
The present invention relates to a vehicular drive shaft assembly adapted for being balanced about an axis of rotation. The vehicular drive shaft assembly includes a drive shaft tube having a first end and a second end, and a first tube yoke including a first radially outer wall fixedly mounted to the first end of the drive shaft tube. A first balance pendulum is located radially inward of the first outer wall and rotationally fixable relative to the first tube yoke, and a second balance pendulum is located radially inward of the first outer wall and rotationally fixable relative to the first tube yoke. Also a second tube yoke is fixedly mounted to the second end of the drive shaft tube.
The present invention also relates to a method for balancing a vehicular drive is shaft assembly comprising the steps of: mounting a first balance pendulum to a first tube yoke; mounting a second balance pendulum to the first balance pendulum; securing the first tube yoke to a first end of the drive shaft tube such that the first and second balance pendulums are located within the drive shaft tube; securing a second tube yoke to a second end of the drive shaft tube; measuring the out of balance of the vehicular drive shaft assembly after the first and second tube yokes have been secured to the drive shaft tube; if the vehicular drive shaft assembly measures out of balance, adjusting the orientation of at least one of the first balance pendulum and the second balance pendulum relative to the first tube yoke in response to the out of balance measurement; and rotationally fixing the first and second balance pendulums relative to the first tube yoke.
An advantage of an embodiment of the present invention is that a vehicular drive shaft assembly can be balanced about an axis of rotation without creating additional stress risers associated with conventional drive shaft balancing.
Another advantage of an embodiment of the present invention is that the vehicular drive shaft assembly can be balanced for rotation about an axis in a relatively simple and accurate manner.
A further advantage of an embodiment of the present invention is that, with the balance weights located inside of the vehicular drive shaft assembly, the weights cannot be thrown off of the assembly during vehicle operation.
Various objects and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiment, when read in light of the accompanying drawings.